1. Field of the Invention
This invention relates to a method of lancing for a copper-producing converter which is used to produce crude copper from a matte.
2. Description of the Prior Art
A copper-producing converter is a furnace in which air or oxygen-enriched air is blown into a molten matte through tuyeres located below the surface of the molten matte to oxidize it to, thus removing iron and sulfur therefrom to produce crude copper. The cycle of its operation is divided into a stage of slag forming and a stage of blister forming. During the stage of slag forming, FeS is oxidized into FeO and sulfur is oxidized into SO.sub.2 and exhausted. If FeO is further oxidized, it forms Fe.sub.3 O.sub.4, but this substance has a high melting point and a high degree of viscosity and is thus undesirable for the operation of the furnace. Therefore, the furnace is charged with a flux, such as solid silica, so that FeO may combine with SiO.sub.2 in the flux to form a slag and be removed. The stage of blister forming follows the stage of slag forming. The molten material from which iron has been separated during the stage of slag forming is further oxidized, and the reactions which may, for example, be expressed by the following equations take place to produce crude copper. Cu.sub.2 S+O.sub.2 =2Cu+SO.sub.2, Cu.sub.2 S+2Cu.sub.2 O=6Cu+SO.sub.2. All of the reactions which take place during the stage of slag forming and blister forming are exothermic. If the molten material has too high a temperature, it is likely to damage the brick lining of the furnace. Therefore, it is usual to introduce a cold charge, such as copper scrap or smoke dust, for controlling the temperature of the molten material, as well as for increasing the production of crude copper.
Insofar as the reactions taking place in the furnace are such that the iron and sulfur in the matte combine with the oxygen in the air blown into the matte, an increase in the oxygen content of the air brings about a reduction in the time required by the reactions and an increase in the amount of heat produced per unit time. If air having a higher oxygen content is employed, it is possible to increase the quantity of the matte treated per unit time and the amount of the cold charge employed. Therefore, the use of air having a higher oxygen content is an effective way to raise the productivity of a copper-producing converter.
If air having a higher oxygen content is blown into the furnace through the tuyeres, however, an increased amount of heat is generated in the vicinity of the tuyeres and greatly damages the brick lining in their vicinity. It is, therefore, understood in the art that oxygen-enriched air having an oxygen content of only up to about 30% can be blown through the tuyeres. It is only to a limited extent that the quantities of the matter and the cold charge can be increased. Moreover, the wear of the brick lining around the tuyerers gives rise to a noticeable reduction in the life of the furnace, even if air having an oxygen content of only about 30% is used.